Brome mosaic virus (BMV) is a small multicomponent RNA virus having interesting structural and biological properties. We have shown that each of the four RNA components of BMV will bind tyrosine (but no other amino acid) in an enzyme and energy dependent reaction similar to that used to charge amino acids to tRNA. Other research groups have shown that RNA from mengovirus will bind histidine, and that RNA from several tymoviruses will bind valine. A host tRNA that is associated with Rous sarcoma virus RNA has been found to function as a primer for reverse-transcriptase-mediated DNA synthesis. Many bacteriophage and viral RNAs contain tRNA-like sequences (-CpCpA or -CpC) at their 3'-termini, and a regulatory role for this end of the molecule seems likely. In this application, experiments are detailed towards evaluating a model in which the aminoacylation property of BMV RNA serves as a recognition site for replicase binding, thereby enhancing its infectivity. This function may be critical when small amounts of viral RNA are present in the host cell, such as in early stages of infection. Prokaryotic elongation factors EF-Tu, EF-Ts are known to constitute two of the four subunits of Q beta replicase. Since it is known that aminoacylated, but not uncharged, viral RNA will bind eukaryotic elongation factor 1 (EF 1), the possibility that this binding provides the required recognition for part of the replicase will be examined. The further postulation that the viral specific subunit(s) subsequently bind to this complex, perhaps directly after translation from the genome, will be tested using cell-free translation systems. Comparision will be made of EF-Tu, EF-Ts, and EF 1 in regard to their function as replicase subunits. The relative efficiency of charged, uncharged, and of the charged viral RNA-EF 1 complex as replicase templates will be compared using in vitro replication systems. In addition, the infectivity of native and chemically modified BMW RNA will be tested in vivo. The possibility of blocking aminoacylation of viral RNA as a basis for resistance or tolerance to viral infection of eukaryotes will be investigated.